The present invention relates to a proces for the production of xylene, more particularly to a process for producing xylene from toluene or benzene in high selectivity by using fluorine-containing crystalline aluminosilicate or fluorine-containing crystalline borosilicate as a catalyst.
Various processes have been known to produce xylene, which is industrially very useful, by methylation of toluene or benzene. For example, a process of methylation in the presence of crystalline aluminosilicates such as ZSM-5 and ZSM-11 is disclosed in Japanese patent application laid-open Nos. 57688/1976 and 120292/1977, and a process of methylation using crystalline borosilicate is disclosed in Japanese patent application laid-open No. 55500/1978.
When, however, these crystalline aluminosilicates such as ZSM-5 are used with no modification as catalysts in the methylation of toluene, undesirable side reactions such as disproportionation are liable to occur. This will lead to a reduction in selectivity of xylene. Furthermore, the crystalline aluminosilicate catalysts are inferior in respect of durability or service life and are not sufficiently satisfactory for practical use.
Similarly, when the crystalline borosilicate catalyst is used as it is, the methylating agent is not effectively used in the methylation reaction and side reactions occur, yielding large amounts of by-products.